The actual single use injection syringes are of the classical piston-pump type. The injection liquid has to be stored separately in an ampoule. Immediately before use the ampoule is opened and the injection liquid is sucked in. In many cases the needle and the injection syringe are packed separately and have to be assembled prior to use. This handling needs some experience and when not correctly done contamination of needle and liquid is possible.
The injection device described in this invention does not need any assembling or filling prior to use. It is easy to produce and to use.
The U.S. Pat. No. 3,736,933 (June 5, 1973) describes already a similar injection packaging formed from flexible plastic tubing with a hollow needle sealed therein. To hinder the flowing out of liquid during storage a breakable normally heat sealed seam of decreasing thickness is positioned between the filled plastic tube and the needle. By finger pressure imposed on the outer walls of the tube the seal bursts and opens the way to the needle. Practical tests revealed that it is very difficult in production to make the seal in a manner that it ruptures correctly without external leakage. Due to the the flexibility over the whole body of the device it is difficult to squeeze it out completely by finger pressure. This hypodermic applicator does not permit aspiration of blood samples which is important for intravenous injections and to take small diagnostic blood samples as will be described later.
The U.S. Pat. No. 2,744,527 (May 8, 1956) describing a syringe-ampoule system where the needle penetrates a membrane prior to injection, or the two parts of a rigid multicompartmented device are separated by a flexible tube closed by a screw, does not interfere with our patent claim.
The U.S. Pat. No. 3,757,981 (Sept. 11, 1973) describes a valve needle syringe system where the valve has to be opened by hand prior to injection.
Finally the U.S. Pat. No. 4,130,117 (Dec. 19, 1978) describes a deformable ampoule with needle where a rupturable membrane extends across the neck portion sealing a medicament in the ampoule. This membrane has an outside tab to break it prior to use. Our patent claims may be distinguished from the forementioned patents because the opening of our flexible injection device is made in both cases (using the pressure release valve or breakable seam) by simple pressure on the outside of the device.